Many locals were dying from disease.

[kadioguy]

Many locals were dying from disease.
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Does it mean "Many locals were going to die because of disease" or "Many locals died one after another because of disease"?

Source: the sentence in paragraph 2, line 2.

 

[teechar]

Does it mean "Many locals were going to die because of disease"

No. It simply means that some disease(s) was killing many people around that time.
There are two justifications for using the past continuous here.

1- When we ask such a question and mention a time of some duration in the past, we can use the past continuous.
Q: What was so notable about 1875?
A: Many locals were dying from disease.

Q: What were you doing at 7:00 PM last night?
A: I was having dinner with friends.

2- When we have two concurrent actions in the past, we can use the past continuous for the longer one and the past simple for the shorter one.
(As) many locals were dying from disease, people carried statues ... and set off fireworks ...".

 

[jutfrank]

To add to teechar's post:

We can use the past continuous to say what was happening at a certain point in time. That is to say, we can describe the situation, or, as I like to say, the 'historical context'. The fact that people were dying adds important situational, historical, contextual, meaning to the events described.

 

[Tdol]

I don't want to get into a complex and volatile history but a search for Taiwan 1874 might help.